Manganese sulfate (manganese is ionically bonded to the sulfate group)
Ingredient name: Manganese Sulfate
Chemical Formula: MnSO4(H2O)
Institute of Medicine Daily Recommended Intake: 1.8 mg (females) 2.3 mg (males)
Amount contained in one pouch of Soylent: 2 mg
Manganese is needed in bone formation, as well as in the metabolism of amino acids, lipids and carbohydrates.
Despite being an essential nutrient (i.e., a total absence of manganese could eventually result in death), manganese deficiency is rarely encountered in humans. As such, a relatively (compared to other nutrients) small quantity of research has been conducted on this mineral.
Manganese's primary function stems from its role as a cofactor in a variety of enzymes, including manganese superoxide dismutase, which initiates the breakdown of harmful types of oxygen (specifically the reactive oxygen species, superoxide). Other manganese-specific enzymes include arginase (a component of amino acid metabolism) and pyruvate carboxylase (carbohydrate metabolism).
Manganese is absorbed in the small intestine and of the total quantity ingested, studies suggest that between 1 and 16 percent is absorbed., Total body manganese levels are estimated to be between 10 to 20 mg. After absorption and filtration in the liver, high concentrations are stored in the liver, kidney and pancreas and approximately 25 percent of manganese is stored in bones.
Reason this form chosen:
Manganese sulfate is a stable form of manganese that also provides a neutral taste profile.
 "Manganese." In Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc, 394. Washington, D.C.: National Academies Press, 2001. http://plk.tn/1IBkq90
 Erdman, J. W., MacDonald, I. A., Zeisel, S. H. "Manganese, Molybdenum, Boron, Chromium, And Other Trace Elements." In Present Knowledge in Nutrition, 587. Washington, DC: International Life Sciences Institute, 2012.
 Ibid., 588
 Ross, C. A., Caballero, B., Cousins, R. J., Tucker, J. L., Ziegler, T. R. "Manganese." In Modern Nutrition in Health and Disease, 241. Baltimore, Maryland: Lippincott, Williams & Wilkins, 2014.